Process of increasing the service life of asphalt



Patented Feb. 1, 1944 PROCESS OF INCREASING THE SERVICE LIFE OF ASPHALTRobert E. Burk, Cleveland Heights, Ohio. assignor to The Standard OilCompany, Cleveland, Ohio, a corporation of Ohio No Drawing. ApplicationMay 2, 1940, Serial No. 333,014

Claims. (01. 106-273) Asphalt although having many advantages of ease ofapplication and highly desirable properties in service, for paving,roofing, and like surfacing conditions, is by reason of such drasticexposure to air and sun given a tendency to soon harden up and becomebrittle and lose its initial desirable properties. A pavement surfacethus may become practically mined in three or four years exposure, andsimilarly the service life of asphalt coating generally is considerablyshortened. I have found that this action is greatly accelerated by thepresence of metal, particularly iron, in the asphalt, the effect thereofbeing of a catalytic order to greatly accelerate the deterioration ofthe asphalt during exposure. Oxidized asphalt is a residual stock andcontains incidental iron from the manufacturing equipment. Any asphalttakes up metal where mixed in a metal pug mill, especially if the timeis long or the temperature much above 350 F. In accordance with thepresent invention it now becomes possible to counteract such catalyticaction in asphalt, and anti-catalytically inhibit the effect of metals,such as iron, which may be present.

To the accomplishment of the foregoing and related ends, the invention,then, comprises the features hereinafter fully described, andparticularly pointed out in the claims, the following descriptionsetting forth in detail certain illustrative embodiments of theinvention, these being indicative however, of but a few of the variousways in which the principle of the invention may be employed.

The asphalt, prepared by any of the known or desired methods, and tosuch specifications of penetration, etc. as desired, is, in accordancewith the invention, treated with the action of an agent which forconciseness I hereinafter designate as a metal anticatalyst.Illustrative of such agent is amino-mercapto-benzothiazole, tetramethyldiamino diphenyl methane, phosphorus, Pass, and oil-soluble naphthenicacid, sulfides of phosphorus having less sulphur, as P4S3, etc. In someinstances, less desirably, sulphur may be employed, it being understoodof course that the sulphur is incorporated after the asphalt has beenbrought to desired specification by the asphaltmaking procedure, whetherby blowing or other a process. In other words, the sulphur is notintroduced into the initial raw material or stock and the latter merelysulphurized.

The iron anticatalyst treatment is advantageous for asphalts prepared byaluminum chloride, as well as asphalts prepared by usual oxidizing orsteam methods. The present treatment is likewise advantageous withnatural asphalts, natural coal tar, etc. The amount of metalanticatalyst required is in general small, ordinarily less than 1 percent and may be preferably 0.01-0.5 per cent. The anticatalyst isintroduced with the asphalt in molten condition, being thoroughlydisseminated in the mass. In some cases also it is advantageous toinclude a so-called oxidation inhibitor, 'the combination peculiarlygiving results out of proportion to those with the individualingredients. The oxidation inhibitor may be employed in amounts of0.01-5 per cent, preferably less than 2 per cent. Illustrative of suchinhibitor is tetra amino diphenyl methane derivatives, acetoacetanilid,pheny1 naphthylamine, quinoline, tetramethylene pentamine,diphenylamine, etc.

As an example: An oxidized asphalt prepared ready for use, is treated bythe incorporation while molten, of 0.25% of amino-mercaptobenzothiazole.This product tested by exposure in a flat bottom glass dish, with airblown upon the surface and with heating at 325 F. for a five hourperiod, showed a loss of penetration amounting to 16.3%. In contrast,the original asphalt, untreated with anticatalyst, similarly tested,showed a loss of 26.2%.

As another example: An oxidized asphalt prepared irom Illinois petroleumbottom stock is treated by incorporation, while molten, of 0.25% ofmercapto-benzothiazole and 0.1% of phosphorus. On test as abovedescribed, this product showed a penetration loss of only 13.5%.

As another example: An oxidized asphalt is treated by incorporating,while molten, 0.05% of phosphorus.

As another example: An asphalt prepared by means of 0.25% of aluminumchloride, to desired final specification, is treated, while molten, byincorporation of 0.05% of phosphorus.

Other modes of applying the principle of the invention may be employed,change being made as regards the details described, provided thefeatures stated in any of the following claims, or the equivalent ofsuch, be employed.

I therefore particularly point out and distinctly claim as my invention:

1. A process of increasing the service-life of asphalt, which comprisesincorporating in processed asphalt containing metal causing accelerateddeterioration on exposure, a metai-anticatalyst selected from the groupconsisting of sulphides of phosphorus, sulphur, andamino-mercapto-benzothiazole, in a small amount sufficient to increasethe service-life of the asphalt against metal action.

2. A process of increasing the service-life of asphalt, which comprisesincorporating in asphalt containing-metal causing accelerateddeterioration on exposure, a small amount each of an oxidation inhibitorand a metal-anticatalyst said anticatalyst being selected from the groupconsisting of sulphides of phosphorus, sulphur, andamino-mercapto-benzothiazole, sufllcient to increase the service-lite ofthe asphalt against metal action and brittlins.

3. A process of increasing the service-life of asphalt, which comprisesincorporating in proc-- essed asphalt containing metal causingaccelerated deterioration on exposure, a small amount of P48: suilicientto increase the service-lite or the asphalt against metal action.

4. A process of increasing the service-life of asphalt, which comprisesincorporating in processed asphalt containing metal causing accelerateddeterioration on exposure, a small amount of a phosphorus sulphidesuflicient to increase the service-life 01' the asphalt against metalaction.

5. A process of increasing the service-life of asphalt, which comprisesincorporating in processed asphalt containing metal capable of cansingaccelerated deterioration on exposure, a small amount or'amino-mercapto-benzothiazole surflcient to increase the service-life oithe asphalt against metal action.

ROBERT E. BURK.

